News

Will the oceans be clean again? - How to search for and identify microplastics in the marine environment using digital holography.

In recent years the pollution of soil and oceans has drastically increased, affecting the food chain and consequently causing damage to plant life, contaminating fauna and damaging human health.

Among the major contaminants, microplastics play a relevant role and even though several techniques have been proposed to analyse the presence of such material in water, the overall data are largely incomplete.
A group of Italian researchers (F. Merola et al.) have proposed using a non-invasive technique based on digital holography to search for and reconstruct the shape of different types of microplastics in water.

They report in the European Physical Journal Plus(EPJ Plus) how it is possible to identify different fragments of the most used types of plastic (such as PET, PVC, PP, PE and PS), which heavily contaminate the seas, and how this high-resolution technique is able to distinguish plastics from organisms such as diatoms, a major group of microalgae living in the marine environment.

Amphiphilic molecules contain both hydrophilic and lipophilic moieties. When in solution they produce structures coming from cooperative interactions of many functional units acting in synergy. Most self-assembling soft matter systems involve strong specific interactions of functional units leading to qualitatively new structures of highly soluble micellar or fibrillar aggregates. In this EPJ E Colloquium, Nyrkova and Semenov focus on the systems with the incorporated into unimer molecules and discuss the effects of packing frustrations and unimer chirality as well as the origins of spontaneous morphological chirality in the case of achiral unimers. They describe several theoretical approaches (overcoming the limitations of weak interaction models) including the concepts of super-strong segregation, geometrical mismatch and orientational frustration. They also review some recently developed phenomenological theories of surfactant membranes and multiscale hierarchical approaches based on all-atomic modeling of packing structures of amphiphilic molecules with strongly interacting groups.

Highest intensities of ultracold neutrons (UCN) are in worldwide demand for fundamental physics experiments. Tests of the Standard Model of particle physics and searches for physics beyond it are performed with UCN.

Two of the leading UCN sources, at PSI and at LANL, are based on solid deuterium (sD2) at temperatures around 5 K. Here, together with NCSU they joined forces to understand UCN intensity decreases observed during pulsed neutron production. The study shows that the decrease can be completely explained by the build-up of frost on the sD2 surface during operation. Pulsed proton beams hitting the spallation targets generate heat pulses causing cycles of D2 sublimation and subsequent resublimation on the sD2 surface. Even very small frost flakes can act as total reflectors for UCN and cause an intensity decrease.

Complexity, as far as information theory is concerned, plays an important role in extracting the amount of uncertainty in dynamics. Several entropy-based measurements have been successfully implemented to quantify the divergence of a system. Uncertainty also plays an effective role, in the field of cryptography, in generating secret keys and to design the most secure model. Recently, real applications have been implemented considering the effect of dynamical complexity, in the field of optical communications, using semiconductor lasers. This EPJ Plus Focus Point edited by Santo Banerjee is a collection of research articles based on the recent developments of communication schemes using chaos and dynamical complexity. The results have been implemented with dynamical models, circuit design, complex networks along with their applications in image, video and optical communications.

The relative position of a particle in relation to the interfacial plane

In this EPJ E Topical Review, Armando Maestro and colleagues unravel the physico-chemical bases underlying the attachment of particles to fluid interfaces. Their focus is on the relaxation mechanisms involved in the equilibration of particle-laden interfaces.

Particle-laden interfaces play a key role in many systems that are used in industrial and technological applications, such as the stabilization of foams, emulsions, or thin films, flotation processes, encapsulation, pharmaceutical formulations, food technology and catalysis.

Adsorption of water molecules on the surface of copper nanoparticles could produce hydrogen faster and more efficiently.

New model explains interactions between small copper clusters used as low-cost catalysts in the production of hydrogen by breaking down water molecules

Copper nanoparticles dispersed in water or in the form of coatings have a range of promising applications, including lubrication, ink jet printing, as luminescent probes, exploiting their antimicrobial and antifungal activity, and in fuel cells. Another promising application is using copper as a catalyst to split water molecules and form molecular hydrogen in gaseous form. At the heart of the reaction, copper-water complexes are synthesised in ultra-cold helium nanodroplets as part of the hydrogen production process, according to a recent paper published in EPJ D. For its authors, Stefan Raggl, from the University of Innsbruck, Austria, and colleagues, splitting water like this is a good way of avoiding splitting hairs.

The drying of complex solutions, such as colloidal dispersions, is a phenomenon of great interest, both scientific and technical, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art. This EPJ E Colloquium discusses a wide variety of problems related to the drying of colloidal systems, from the stabilization of dairy products to cracking phenomena that occur at the surface of planets or on an oil painting. The diversity of these processes lies in the great variability in size and/or time scales and makes it very hard to understand and analyse the mechanisms at play. The results presented in this review attest to the reliability of experimental modelling in the laboratory, a clever way to use the drying of complex fluids to reproduce and study original mechanisms.

DNA and RNA are naturally polarised molecules containing electric dipole moments due to the presence of a significant number of charged atoms at neutral pH. Scientists believe that these molecules have an in-built polarity that can be reoriented or reversed fully or in part under an electric field—a property referred to as bioferroelectricity. However, the mechanism of these properties remains unclear. In a new study published in EPJ E, See-Chuan Yam from the University of Malaya, Kuala Lumpur, Malaysia, and colleagues show that all the DNA and RNA building blocks, or nucleobases, exhibit a non-zero polarisation in the presence of polar atoms or molecules such as amidogen and carbonyl. They have two stable states, indicating that DNA and RNA basically have memory properties, just like a ferroelectric or ferromagnetic material. This is relevant for finding better ways of storing data in DNA and RNA because they have a high capacity for storage and offer a stable storage medium. Such physical properties may play an important role in biological processes and functions. Specifically, these properties could also be extremely useful for possible applications as a biosensor to detect DNA damage and mutation.

Differential operators with non-singular kernels have been suggested recently and have raised interest in many fields of science, technology and engineering. They have being recognized to have brought news tools in applied mathematics and other applied sciences, as they are able to capture and observe a more complex physical behavior of nature. One of their unique properties is crossover behavior; in particular, their ability to capture Brownian motion, stochastic processes, anomalous diffusion and power-law dependency processes. This Focus Point on Modelling Complex Real-World Problems with Fractal and New Trends of Fractional Differentiation edited by A. Atangana, Z. Hammouch, G. Mophou and K. M. Owolabi in EPJ Plus aims at capturing current developments and initiatives of these new mathematical tools in modeling real-world problems. It focuses on new numerical and analytical methods for solving the complex real-world problems arising in physics. Several new results were presented and published in this Focus Point. In particular, a revolutionary paper has led to the extension of the field of non-local operators and their applications. The particular attention devoted to these new mathematical tools leaves no doubt on the fact that the future of modeling real-worl problems relies on these operators.

Physicists develop improved algorithms for simulating how complex molecules respond to excitation by photons, and explaining what happens when photons hit our eyes

What makes it possible for our eyes to see? It stems from a reaction that occurs when photons come into contact with a protein in our eyes, called rhodopsin, which adsorbs the photons making up light. In a paper published in EPJ B, Federica Agostini, University Paris-Sud, Orsay, France, and colleagues propose a refined approximation of the equation that describes the effect of this photo-excitation on the building blocks of molecules. Their findings also have implications for other molecules, such as azobenzene, a chemical used in dyes. The incoming photon triggers certain reactions, which can result, over time, in dramatic changes in the properties of the molecule itself. This study was included in a special anniversary issue of EPJB in honour of Hardy Gross.